Respiratory Filters

Particle filters provide reliable protection against particulates and aerosols, e.g. dust, fumes, micro-organisms and viruses. This type of filter is labelled with the letter P according to the EN 143 standard and rated based on its filtration efficiency, known as particle class. The particle or filter class indicates how efficiently particles are filtered from the air and gives an indication of the maximum occupational exposure limit (OEL) up to which the filter should be used. Find out more:

Class 1 or P1:

• Particle filter class with lowest efficiency
• Filters at least 80% of airborne particles
• Max. 4x OEL value w. both half and full face masks¹
• Offers protection against solid particles that are not specifically toxic
• Use for e.g. calcium carbonate or zinc oxide

Class 2 or P2:

• Particle filter class with intermediate efficiency
• Filters at least 94% of airborne particles
• Max. 10x OEL value w. half masks and 10x OEL value w. full-face masks¹
• Offers protection against hazardous and irritant airborne particles in solid and/or liquid form
• Use for e.g. silica or sodium carbonate

Class 3 or P3:

• Particle filter class with high level of efficiency
• Filters at least 99.95% of airborne particles
• Max. 20x OEL value w. half masks and 40x OEL value w. full-face masks¹
• Offers protection against toxic airborne particles in solid and/or liquid form
• Use for e.g. beryllium or nickel

¹ _{always check domestic OEL recommendations and local regulations before filter configuration and use}

The filter class or filter grade indicates the respective absorption capacity of gas filters for specified groups of hazardous gases and vapours. Filters in higher classes are suitable for protection against higher gas concentrations in the working environment. Filter classes are exclusively used for gas categories A, B, E and K.

Class 1:

• Gas filter class with lowest capacity
• Max. concentration for capacity test according to standard 0.1% by volume (1,000 ppm)
• Max. 30x OEL value w. half masks and 400x OEL value w. full-face masks
• e.g. A1 filter for organic gases and vapours

Class 2:

• Gas filter class with medium capacity
• Max. concentration for capacity test according to standard 0.5% by volume (5,000 ppm)
• Max. 30x OEL value w. half masks and 400x OEL value w. full-face masks
• e.g. A2B2 filter for organic and inorganic gases and vapours

Class 3:

• Gas filter class with largest capacity gas filter
• Max. concentration for capacity test according to standard 1.0% by volume (10,000 ppm)
• Usually worn on the body and not directly on the mask due to significant size of cartridge
• Dräger does not offer class 3 gas or combination filters for respiratory mask or powered respirators

For AX, Hg or Reactor filters, designed for more specialized applications or less common contaminants, no analogue filter class ratings are specified. Instead, these filter types have specified maximum operating times due to technological factors limiting their respective absorption capacity. The maximum operating time for corresponding filters depends on the contaminant concentration or, in case of reactor type filters, on the level of radioactivity:

• AX filters are limited to between e.g. 20 and 60 minutes of use, depending on contaminant concentration, and approved for single use only
• Hg filters have a maximum permissible operating time of 50 hours, approved for reuse if Hg contaminant is not present during use
• Reactor filters have no generally formulated maximum operating times, and are subject to national regulations and domestic radiation limits

For CO or NO protection, filters in the form of catalytic converters are required, which have no retention or filtering capacity of their own but convert hazardous gases such as carbon monoxide or nitrogen oxides into harmless reaction products by means of catalysis. Once this process has been initiated, the catalysis can no longer be stopped and the filter is continuously consumed. Accordingly, these filters are not authorized for multiple use and may only be used for a specified period of time. Combination filters with a CO or NO component can be reused unless the respective contaminant is present during reuse, which precludes reuse.

• CO filters are approved for single use only and have a maximum operating time given in minutes, e.g. 20 minutes for a CO 20 filter
• NO filters have limited operating times depending on contaminant concentration, and are approved for single use only 

Filter classification for gas filters and combination filters are detailed in the EN 14387 standard. The filter capacity for each filter type can be found in the corresponding IFU from Dräger. For combination filters, the combination values for both filter classes and their underlying OEL values, filter capacities and or filter efficiencies are applicable.

All types of respirator filters are marked with the standard EN 14 387 colour codes used throughout the European Union and other countries following the same standard. Colour codes allow you to easily identify the type of protection offered by each filter. The colour coding found on the label of the respective filter indicates the group of gases covered for both gas filters or combination filters, and or the level of particulate protection offered for either particle filters or combination filters. For more information, follow our guide to respiratory filter codes:

• 🟫 AX (Brown): Gases and vapours of organic compounds (boiling point ≤ 65 °C), e.g. methyl acetate, acetone
• 🟫 A (Light Brown): Gases and vapours of organic compounds (boiling point > 65 °C), e.g. acetic acids, acrylics
• 🌫️ B (Grey): Inorganic gases and vapours, e.g. chlorine, hydrogen sulphide or hydrogen cyanide²
• 🟨 E (Yellow): Acid Gases and vapours, e.g. sulphur dioxide, hydrogen chloride and formic acid
• 🟩 K (Green): Ammonia and organic ammonia derivatives, e.g. hydrazine, methylamine and aziridine
• ⬛ CO (Black): Carbon monoxide
• 🟥 Hg (Red): Mercury vapours
• 🟦 NO (Blue): Nitrous gases and vapours, including nitrogen oxides
• 🟧 Reactor (Orange): Radioactive iodine, including radioactive methyl iodide 
• ⬜ P (White): Particles

Multi gas filters that cover different gases, or combination filters that provide additional protection against partciles, thus have several colour codes and a compound label. An A2B2E2K2 filter e.g. has the following colour code 🟫🌫️🟨🟩, which indicates that the filter provides protection against gases and vapours of organic and inorganic compounds as well as sulphur dioxide, hydrogen chloride, ammonia and organic ammonia derivatives. An A1 P2 combination filter e.g., will in turn be marked with the following colour scheme 🟫⬜ to signify that it offers protection against gases and vapours of organic compounds and particulate hazards.

² _{except carbon monoxide, which is covered by the seperate CO category}

The choice of the right respiratory filter should always be based on a detailed hazard assessment. The following factors in particular should be taken into account during the selection process:

• Preceding hazard assessment: Identify the type of contaminant or contaminants, e.g. organic vapours, acid gases or particulate pollutants such as aerosols, fumes and dusts, and select the appropriate type of filter. The VOICE database from Dräger is a good starting point for your research, providing information on hazardous substances and recommendations for suitable types of respirator filters. Alternatively refer to our Filter Selection Guide or consult a Dräger safety specialist.
  
  
• Contaminant concentration levels: Determine the concentration of contaminants based on the hazard identification to select an appropriate filter class. Compare either the filter efficiency rating for your particle filter (P1, P2 or P3) and or the capacity rating of your respective gas or combination filter (Class 1, Class 2 or Class 3) with the contaminant concentration determined in accordance with the occupational exposure limit (OEL). Similarly, for catalytic gas filters, the maximum allowable operating time must be taken into account.
  
  
• Ambient oxygen levels: Ensure that the oxygen content in your working environment is stable and sufficient, i.e. always at least 19.5%. At lower oxygen concentrations in the ambient air, the use of an air-purifying respirator is not permitted and it is strongly recommended to consider use of a self-contained respirator solution, such as a SCBA, CCBA or an airline system.

This choice will depend on your individual use case and possibly on the type of filter selected for your application. Most respirator filters from Dräger come either as proprietary bayonet filters for half or full masks with a twin filter configuration, or as universal threaded filters for use with single port half or full masks. Some specific filters for more specialized applications may only be available with a certain filter connection type, which in turn determines the mask configuration. For some more complex and therefore heavier combination filters, the use of a full face mask is recommended due to the better weight distribution compared to use with a half mask. In addition to these considerations, both Dräger filter mounts offer a number of unique benefits:

Single filter mask designs & X-plore Rd40 filters: 

• Universal threaded connection for use with either Dräger or third party filters
• Easy filter installation procedure thanks to round thread
• Wide selection of both more common and highly specialized filters
• Robust aluminum filter housing for demanding applications

Twin filter mask design & X-plore Bayonet filters: 

• Proprietary bayonet mount for use with Dräger filters exclusively
• Balanced weight distribution thanks to twin filter configuration
• Unobstructed field of vision thanks to lateral filter mount
• Simple retrofit of add. particle filter pads for gas filters

A P3 filter is a type of particle filter that provides protection against particulate hazards and aerosols, e.g. dust, smoke, microorganisms and viruses. The letter 'P' represents the particle class and designates the type of filter. The number '3' after the letter indicates the filter class, which specifies the filtration efficiency for particle filters. A corresponding filter carries the colour code ⬜ for easy identification. P3 filters have the highest filtration efficiency and provide the best protection against particulate contaminants. They filter at least 99.95% of airborne particles from the ambient air and offer reliable protection against toxic airborne particulates in solid and/or liquid form, e.g. contaminants such as beryllium or nickel.

The letter 'A' on a filter label indicates that this filter offers protection against gases and vapours of organic compounds with a boiling point > 65 °C. The second letter 'P' signifies that the filter provides protection against particulate hazards. An A2 P3 filter is therefore a combination filter. It provides combined protection against both particles and gases of this category. A corresponding filter carries the colour code 🟫⬜ for easier identification. The number '2' behind the letter 'A' identifies the filter class, which indicates the absorption capacity of the gas filter, while the number '3' after the letter 'P' marks the respective filter class, which specifies the filtration efficiency of the particle filter.

The letters 'A', 'B', 'E' and 'K' on a filter label indicate that the filter offers protection against different groups of gaseous contaminants. An ABEK filter is therefore a multi-gas filter that provides protection against gases and vapours of organic compounds, labelled 'A', and inorganic compounds, labelled 'B', as well as acid gases and vapours, labelled 'E', and ammonia and organic ammonia derivatives, labelled 'K'. A corresponding filter also bears the colour code 🟫🌫️🟨🟩 for these gas categories for quick and easy identification. The numbers from 1 to 3 immediately following the letters indicate the filter class, which specifies the absorption capacity of a gas filter, e.g. A2B2E2K2.

The letters 'NR' are the abbreviation for non reusable and indicate that a particle filter is for single use only. A respective filter can only be used for the maximum duration of one work shift. This classification is defined in the EN 143 standard.

The letter 'R' stands for resuable and signifies that a particle filter is certified for reuse, Corresponding reusable filters can therefore be used for more than one working shift. The filter should be stored properly between uses, i.e. well protected from moisture and temperature. This classification is also defined in the EN 143 standard.

Some particulate filters may be additionally labelled with the letter 'D'. This indicates that the filter has successfully passed the optional dolomite dust test. The test procedure assesses the performance of the filter against clogging and ensures that the breathing resistance of the filter remains low even over extended periods of use and in high-dust environments. This classification is defined in EN 149.

A general guide value for the filter lifetime or service life of filters cannot be given, as the service life span depends heavily on factors such as the respective filter type and ambient conditions, e.g. the type and concentration of the contaminant, occupational exposure limits and climate related factors such as humidity and temperature. For some groups of gas or combination filters including Hg or AX filters, or gas or combination filters that include catalytic converters as part of the filter configuration, e.g. CO or NO, service lifetimes are limited to a specified period of time detailed in the respective IFU. Accordingly, these filters are not authorised for multiple use.

Mask filters should always be replaced when one or more of the following points apply: increased breathing resistance for particle or combination filters, noticeable taste or smell for gas or combination filters, damage or contamination of the filter used or expiration for all types of filters. 

However, the shelf life of filters can be determined provided the original packaging is undamaged and the storage conditions are met. For the X-plore Rd40 mask filters, Dräger gives a shelf life of 6 years for gas and combination filters and 12 years for particulate filters, from the date of manufacture. For the X-plore Bayonet filter series, Dräger gives a shelf life of 6 years for all gas and combination filters, 12 years for particle filters, 3 years for filter pads and 4 years for pure filters, from the date of manufacture.

The service life of a respirator filter and the frequency of filter replacement depend on several factors, including the concentration of contaminants, the duration of use and the specific type of respiratory filter used (e.g. particle filter, gas filter, combination filter). Mask filters should always be replaced when one or more of the following points apply: increased breathing resistance, noticeable taste or smell, damage or contamination of the filter used or expiration. 

We advise you to replace the respirator filter in the following cases:
• If you find it increasingly difficult to breathe³. This may indicate that the filter is clogged.
• If you begin to taste or smell a contaminant⁴. This indicates that the filter is saturated and no longer effective.
• If your filter is physically damaged or contaminated. Immediately replace the filter to avoid all risk.
• If your filter has reached its expiry date. Replace the filter as proper performance can no longer be ensured.

Remember that timely filter replacement is critical to the protection of your respirator. Please strictly follow the guidelines provided by Dräger for your specific filter type, which can be found in the relevant instruction manual.

³ _{applies only to particle filters or particle filtering components of combination filters}
⁴ _{applies only to gas filters or the gas cartridge component of combination filters}